1. Field of the Invention
The present invention relates to controlling a defrosting operation of a refrigerator, and more particularly to a method of learning a refrigerator use pattern so that the defrosting operation is carried out at a point of time when is not in use the refrigerator.
2. Description of the Prior Art
Generally, refrigerators perform freezing and refrigerating operations by driving compressors for a predetermined period and then defrosting operations for defrosting freezing chambers by actuating defrosting heaters. The defrosting period for such defrosting operations is controlled, depending on the freezing period and the refrigerating chamber temperature.
FIG. 1 is a block diagram of an operation control apparatus for a general refrigerator. As shown in FIG. 1, the operation control apparatus comprises an electric power supply unit 1 for supplying electric power to required units of the operation control apparatus, a compressor driving unit 3 for driving a compressor (not shown) for generating cold air, a cooling fan driving unit 4 for driving a cooling fan (not shown) for blowing the cold air into a freezing chamber and a refrigerating chamber of the refrigerator, a damper driving unit 6 for driving a damper (not shown) for opening and closing a passage of the cold air introduced in the freezing and refrigerating chambers, a heater driving unit 6 for driving a defrosting heater (not shown) for generating heat and thus defrosting the freezing chamber, a temperature sensing unit 7 for sensing temperatures of the freezing and refrigerating chambers by means of temperature sensors disposed in the freezing and refrigerating chambers, and a door opening/closing sensing unit 8 for sensing the opening and closing of the freezing and refrigerating chambers. The operation control apparatus also comprises a central processing unit 2 for controlling the compressor driving unit 3, the cooling fan driving unit 4, the damper driving unit 5 and the heater driving unit 6, in response to sensing signals from the temperature sensing unit 7 and door opening/closing sensing unit 8, and thus controlling the operation of the refrigerator.
Now, a conventional method for controlling a defrosting operation of the refrigerator with the above-mentioned operation control apparatus will be described, in conjunction with FIG. 2.
FIG. 2 is a flowchart of a procedure for controlling the operation of refrigerant in accordance with the prior art.
As shown in FIG. 2, electric power is applied to the refrigerator, the central processing unit 2 drives the compressor driving unit 3 and the cooling fan driving unit 4, so as to drive the compressor and the cooling fan. The central processing unit open damper by driving the damper driving unit 5 so that a cooling operation step for introducing cold air in the chambers of the refrigerator is carried out.
Thereafter, the central processing unit 2 counts the driving period of the compressor, that is, the cooling operation period and performs a step of determining whether the counted period corresponds to a predetermined period. Generally, a defrosting operation is carried out to defrost the freezing chamber, after a predetermined cooling operation period during which the compressor of refrigerator is driven lapses. The predetermined cooling operation period corresponds to a predetermined period for determining whether the sum of the periods during which the compressor is driven corresponds to a period after which a defrosting operation should be initiated.
If the counted period does not reach the predetermined period after which the defrosting operation is initiated, the central processing unit 2 then determines whether the chamber temperature sensed by the temperature sensing unit 7 reaches a predetermined minimum temperature. When the chamber temperature does not reach the predetermined minimum temperature, the central processing unit 2 performs a step of returning the procedure to the step of counting the compressor driving period.
When the chamber temperature has reached the predetermined minimum temperature as it is continuously lowered by the continued driving of the compressor, the counting of the compressor driving period is stopped, while keeping the counted value indicative of the period during which the compressor is driven. Simultaneously, the central processing unit 2 carrier out a step of turning off the compressor and the cooling fan and closing the damper.
After the compressor and the cooling fan are turned off, the central processing unit 2 determines whether the chamber temperature of the refrigerator has reached a predetermined maximum temperature. If the chamber temperature has reached the predetermined maximum temperature, the compressor and the cooling fan are turned on again and the procedure is returned to the step of carrying out the cooling operation. When the the compressor and the cooling fan are not driven, the chamber temperature increases, since the door of the refrigerator is often opened or the chambers of refrigerator is maintained at an imperfect thermal insulation state, even though the door is closed. Accordingly, the cooling operation is automatically initiated again in a manner as mentioned above, when the chamber temperature of refrigerator increases to the predetermined maximum temperature.
If the counted period indicative of the compressor driving period reaches the predetermined period, the counting of the compressor driving period is then initialized. At the same time, the central processing unit 2 turns off the compressor and the cooling fan and closes the damper. The central processing unit also turns on the defrosting heater by driving the heater driving unit 6, so as to perform the defrosting operation.
If a determination is made that the defrosting has been completed after the defrosting operation for a predetermined period, the central processing unit 2 then turns off the defrosting heater and returns to the cooling operation step.
Generally, the control of the chamber temperature of refrigerator is carried out in such a manner that when a predetermined chamber temperature is set to a desired temperature by the user, a predetermined maximum temperature and a predetermined minimum temperature which are obtained by adding positive and negative temperature tolerances to the predetermined chamber temperature, respectively, are stored in the central processing unit, as shown in FIG. 3. When the chamber temperature of the refrigerator is sensed as having been increased up to the predetermined maximum temperature, the central processing unit turns on the compressor, so as to achieve the cooling operation. As the chamber temperature is decreased to the predetermined minimum temperature, by the cooling operation, the central processing unit turns off the compressor, so as to stop the cooling operation. That is, the central processing unit controls the operation of refrigerator by repeating the operations of turning on/off the compressor.
As apparent from the above description, the temperature control is achieved by turning on/off the compressor and the cooling fan so that the chamber temperature of refrigerator and maintained between the predetermined maximum temperature and the predetermined minimum temperature. On the other hand, the defrosting operation is achieved by counting the periods during which the compressor is maintained at its ON state, summing the periods and driving the defrosting heater for a predetermined driving period when the summed time corresponds to a predetermined time.
However, such a control for the defrosting operation has a disadvantage that the defrosting operation is carried out irrespective of whether the refrigerator is being used by the user, since the point of time when the defrosting operation should be initiated is simply determined by the time obtained only by summing the periods during which the compressor is maintained at its ON state.
Assuming that the periods that the user frequently uses the refrigerator, that is, frequently opens the door of refrigerator are the period T1 from 6:00 to 9:00, the period T2 from 11:00 to 13:00 and the period T3 from 17:00 to 20:00 and that the defrosting operation initiating time point based on the sum of the compressor driving periods is the time point t1, the compressor is controlled to be forcibly turned off at the time point t1, as shown in FIG. 3. The defrosting heater is turned on at the time point t1, to initiate the defrosting operation.
Since the chamber temperature increases as the defrosting operation is carried out, the chamber temperature exceeds the predetermined maximum temperature beginning at timepoint t2. Furthermore, when the door of refrigerator is opened by the user during the defrosting operation, the chamber temperature increases sharply to a level at which a desired refrigerating temperature can not be obtained, since the period that the defrosting operation is carried out is included in the period T2 which is one of the periods that the user frequently uses the refrigerator. The chamber temperature can be decreased to the predetermined maximum temperature satisfying the desired refrigerating temperature only at the time point t3 corresponding to a certain time after the period T4 passe, that is, after the defrosting operation was completed and the compressor was driven.
Actually, the increase in chamber temperature during the defrosting operation is higher than the natural increase in chamber temperature, due to the operation of defrosting heater. That is, when the defrosting operation is carried out during the period that the user frequently uses the refrigerator, the chamber temperature is increased to a greatly higher temperature, as compared with the case that the door of the refrigerator is frequently opened under the condition that no defrosting operation is carried out. This is because the temperature increase caused by the defrosting operation is added to the temperature increase caused by the refrigerator door opening. As a result, the chamber temperature is excessively increased and can not be decreased to the predetermined maximum temperature or below while the defrosting operation is continued. Consequently, there is a problem that the chamber temperature can not be maintained at the predetermined temperature desired by the user.